The invention relates to an apparatus for rotatably mounting a rotor to be balanced.
Such an apparatus is known from European Patent Publication No. EP 1 936 347 A2. The known-rotatable mounting, which is embodied as an articulated shaft mounting in a balancing machine, includes spring-loaded support of a vibrating upper part. The latter includes a rotatably mounted spindle with a chuck for clamping one end of an articulated shaft, and a motor for driving the spindle. The spring bars are aligned parallel to the rotational axis and arranged in equal numbers in two parallel vertical planes that are equidistant from the rotational axis of the spindle. At least two spaced-apart groups of spring bars are provided in each plane. The stiffness of the spring bars in the axial direction is at least 100 times greater than their radial bending stiffness. The aim is to be able, by this means, to measure supercritical unbalances on the rotor in a broad range of resonance-free rotation speeds.
Driving the rotor to be balanced directly with a motor and disposing the motor between leaf springs or compression springs that support the motor and the rotor so that they are able to vibrate, is known from EP 0 410 331 A2.
The object of the present invention is to provide an apparatus of the kind initially specified for rotatably mounting a rotor to be balanced, said apparatus having a compact structure and permitting unbalance to be measured in a broad range of rotational speeds free of resonance.
In this invention, the rotatably mounted balancing spindle with which the rotor to be balanced is to be non-rotatingly connected is mounted, via a plurality of spring bars aligned parallel to the spindle axis, to at least one bearing block such that the balancing spindle is able to vibrate. During measurement of unbalance, the balancing spindle is driven by a drive mechanism, in particular by an electric motor. The spring bars are arranged in more than two planes spaced at different distances from the spindle axis, or in planes having different rotary angular positions about the spindle axis. The planes at different distances from the spindle axis are preferably arranged parallel to each other and may be equidistant from each other. The plurality of planes preferably intersect at right angles.
When the spring bars are arranged in the planes having different rotary angular positions about the spindle axis, said planes are preferably at equal angular distances from each other.
The spring bars may be arranged on different circumferences about the spindle axis, the circumferences preferably being radially equidistant from each other. It is also possible to arrange all the spring bars on one circumference, preferably at equal angular distances from each other.
The spring bars preferably have circular cross-sections. However, cross-sections differing from the circular are also possible, in particular rectangular, square or sector-shaped cross-sections for the spring bars.
Due to the spring bars, the balancing spindle is mounted on the bearing block in a largely isotropic (semi-isotropic) manner. It is preferred that the balancing spindle mounted via the spring bars on the bearing block is embodied as a single-plane flywheel in a plane perpendicular to the spindle axis, and is able to vibrate. The unbalance is preferably measured in the supercritical range of the mounting that is able to vibrate. For this purpose, the one ends of the spring bars are rigidly connected to the bearing block, and the other ends of the spring bars are connected to a rigid frame that is able to vibrate and which bears the balancing spindle, so as to form the single-plane flywheel. The spring bars are preferably connected by screw connections to the bearing block and to the rigid frame that is able to vibrate. However, it is also possible to connect the ends of the spring bars integrally, by welding or in some other way, to the bearing block or to the rigid frame that receives the rotatable mounting of the balancing spindle.
A mechanism that alters the resonance of the vibrating system, more specifically a vibration damping mechanism, is preferably provided between the bearing block and the frame that is able to vibrate and which rotatably bears the balancing spindle. This causes damping or reduction of the amplitudes of the vibrating system when the speed of the rotor to be balanced passes through the resonance range of the vibrating system, e.g. when increasing the speed into the supercritical resonance range in which the unbalance is being measured.
In addition, a torque support which is torsionally resistant about the spindle axis and flexible in at least the measuring direction is preferably provided between the bearing block and the balancing spindle. The direction of measurement is oriented perpendicular to the spindle axis.
The electric drive for the balancing spindle is preferably configured in such a way that the balancing spindle is disposed coaxially in relation to the rotor of the electric motor and is preferably connected non-rotatingly to the rotor of the electric motor. To this end, the balancing spindle may be non-rotatingly connected to the rotor in an axial recess or in an axial cavity through the rotor of the electric motor. Electrical insulation may be provided between the housing of the electric drive mechanism, in particular of the electric motor, and a clamping device provided on the balancing spindle for the rotor.
In order to measure the unbalance of elongate rotors, in particular cardan shafts, each end of the elongate rotor is preferably mounted in a rotatable mounting. To adapt the apparatus to different lengths of rotor, the respective bearing block of the rotatable mounting may be axially adjustable in relation to the spindle axis. Another rotatable mounting with the same arrangement of spring bars as with the rotatable mounting on the rotor end, and forming a centre mounting between the two rotatable mountings at the rotor ends, may also be provided in a preferential manner for the elongate rotor. However, said centre mounting does not include a drive mechanism.
In this invention, the ratio of the axial stiffness of the balancing spindle mounting to its radial stiffness may reach values in excess of 1000.